The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Hydraulic fracturing processes are used to, among other things, extract subterranean oil. These processes require significant amounts of water to operate. A single oil or gas well may require three to thirteen million gallons of water. Land-based hydraulic fracturing sites currently utilize locally-sourced fresh water, placing an enormous, unsustainable strain on the local water table.
Currently, areas of significant drilling, such as Texas, have devoted as much as ten percent of local fresh water usage to drilling and hydraulic fracturing operations. According to the Texas Water Development Board and the Railroad Commission of Texas, the State's oil and gas regulator, in 2011, Texas used a greater number of barrels of water for oil and natural gas fracking (approximately 632 million) than the number of barrels of oil produced (approximately 441 million). Water consumption is expected to rise as drilling operations expand. For example, by 2035, the U.S. Energy Information Administration expects nearly 80% of the 21 trillion cubic feet of natural gas produced annually to be from “unconventional” sources such as hydraulically fractured shale. Furthermore, such processes stress arid, fragile ecosystems because many of the most oil-rich portions of the United States (e.g., Eagle Ford Shale and the Permian Basin) are the driest. Some average less than 21 inches of rainfall a year. The current rate of land-based hydraulic fracturing, notwithstanding projected growth, cannot be sustained using fresh water alone.
Hydraulic fracturing processes, also known as “fracking,” “fracing,” or “fraccing,” are used to release hydrocarbons and other substances contained in subterranean rock formations via high pressure injection of a fracturing fluid, such as fresh water, into the rock formation.
In recent years, hydraulic fracturing has been widely used to access previously unreachable deposits of oil and natural gas. As of 2010, 60% of all new oil and gas wells worldwide were created using hydraulic fracturing. Because vast amounts of formerly inaccessible oil and gas can be extracted using hydraulic fracturing, it is likely that usage of such processes will increase in the future.
The fracturing fluid comprises water and low concentrations of chemical additives, depending on the characteristics of the water and the rock formation being fractured. For example, the fracturing fluid may comprise so-called slickwater additives, adapted to reduce friction, allowing the fracturing fluid to be pumped into the fracture at a higher rate than if water alone were used. Slickwater additives typically make up less than two percent of the fracturing fluid and must be adjusted for each rock formation or “play.” Borate salts and potassium chloride (a metal halide salt commonly used as a substitute for table salt) are also common fracturing fluid additives.
After injection, a portion of the fracturing fluid returns to the surface. Such returning fluid is known as “produced water.” Produced water, generated from hydraulic fracturing or normal production of oil and gas wells, typically has a higher concentration of salt, other compounds, elements, and impurities. Produced water may be re-used in the hydraulic fracturing process, however only 40-50% of initially-injected fracturing fluid returns to the surface. Therefore, additional fracturing fluid must be continually added even when produced water is reused. Because of its heavy salinity and impurity concentration, produced water must be removed, cleaned, or reused. Most often, produced water is re-injected into disposal wells or re-injected into injection wells used to maintain the reservoir pressure.
Hydraulic fracturing has been used to create offshore oil wells. For example, large hydraulic fracturing vessels have been employed to open wells in the North Sea, the Arabian Sea, off the western coast of Africa and off the Unites States Gulf Coast. Initially, offshore hydraulic fracturing processes used fracturing fluids comprising fresh water. Fresh water proved to be a major limitation because it was carried out to sea via tankers with limited cargo capacity. Later offshore hydraulic fracturing processes began utilizing a fracturing fluid comprising seawater. Seawater is simply collected from the surrounding ocean, processed, and injected into the fracturing site, thereby eliminating the production bottleneck of a limited fracturing fluid supply.
Given the foregoing, systems and methods for transporting seawater from a plentiful source (e.g., an ocean, saltwater lake, brine source, and the like) to a hydraulic fracturing site are needed. Additionally, systems and methods for transporting, processing and utilizing produced water generated during hydraulic fracturing processes are needed. Systems and methods for transporting seawater and produced water to areas with plentiful resources for de-salinization, additional hydraulic fracturing sites, storage areas, and processing areas, are needed.